In order to develop the chest it is standard practice for the person in training to lie down on his or her back on a weight table. Barbells are then lifted off crutches flanking the table and are raised slowly from a position with the bar lying on the chest of the exerciser to a position elevated above the user's chest with the arms extended.
Such a procedure is disadvantage for two main reasons. First of all it is impossible to tailor the force to the extension. Exercises are preferred which demand less force when the joints involved are less flexed and more force when the limbs are straighter and less liable to dangerous torsions. In addition it is possible for the person exercising to drop the barbell on him or herself, an accident that can be particularly serious when it is considered that a good weight lifter can bench press much more than his or her own weight.